Many combustion processes require either pilot flames or complicated controllers to control ignition and combustion. For example, a gas stove requires either a pilot light or an electric starter. Complex electronics control intermittent spark release in a gas turbine engine to regulate the stability of combustion. While piezoelectric materials have been developed for a variety of ignition systems, in most cases, generation of a voltage across the materials has been controlled almost independently of the flow of the material to be ignited.
For example, Home, in U.S. Pat. No. 5,375,585, teaches a piezoelectric igniter and safety valve for a gas stove. However, the safety valve is controlled by a thermocouple. The igniter is controlled by a knob connected to a valve and a metal striker. As the knob is turned, it first opens the valve, allowing gas to flow, and then causes the striker to hit a piezoelectric element. A voltage is produced across the piezoelectric element, which is then conducted to an electrode, whereat a spark is produced which ignites the gas. A similar process is disclosed by Nelson in U.S. Pat. No. 4,954,078. Nelson discloses an igniter for a propane torch or like device, wherein the igniter is contained within the torch. A valve is opened to permit gas flow, and a trigger is pressed to actuate a spring-loaded plunger which impacts a piezoelectric element. Suzuki, in U.S. Pat. No. 3,986,061, describes an ignition system for cigarette lighters and similar devices in which voltage is generated across a piezoelectric element in response to a bending stress. Again, this voltage is eventually used to generate a spark and ignite a combustible material.
Nelson, in U.S. Pat. No. 5,536,990, describes a system in which one combustion process initiates a subsequent process. The first process includes a detonation which impacts a piezoelectric element. The voltage generated across the element is used to initiate a second process.